One aspect of the first NVR overhaul was the replacement of the cylinder linings.

Linings are made to exactly the diameter of the cylinder (or piston valve) in which they are to be fitted. In order to get them into the cylinder they are shrunk by immersing them in liquid nitrogen and then, while cold, they are slid into their new home.

The photo sequence below, from Engineering Manager Alan Whenman’s collection, shows the steps involved.

Action begins as liquid nitrogen is piped into a large open-topped vacuum flask. Whenever it make contact with air, it evaporates, creating a cloud. In the background can be seen the front of the loco, cylinders with fronts removed.

Soon, the clouds disperse and a final top-up is poured into the flask.

The liner is lowered slowly into the flask. Note everyone is wearing gloves. The temperature is around minus 196°C and contact with skin would result in ‘cold burns’

After about 15 minutes, the liner is completely chilled and can be lifted out of the flask.  It must be inserted into the cylinder within about 30 minutes, otherwise it will begin to warm and expand.